When scrapped automobiles are shredded to recover ferrous and non-ferrous metals, large quantities of non-metallic solid waste are generated consisting mainly of rubber and plastic materials. The disposal of this material presently requires the use of valuable land-fill sites and constitutes the waste of potentially valuable resources. Pyrolysis, i.e., thermal decomposition in the absence of oxygen, of these mainly organic wastes into char and gaseous and liquid chemicals is one approach to an ecologically responsible as well as a profitable means of recycling both energy and chemical materials.
Pyrolyzed shredder waste has been shown to yield substantial amounts of highly aromatic pyrolysis oil from which chemical materials such as benzene, toluene and xylene can be produced. Generally, however, the liquid products produced from this pyrolytic conversion are used as fuels oils, i.e., for their energy content. The gaseous products produced by such processes are often simply combusted prior to release into the atmosphere. Advantageously, these gases have been burnt to generate heat for the pyrolytic process.
However, these oil and gaseous products generally contain undesirable conversion materials, which need to be removed in order to make these products suitable for use as described above. Attempts made to clean up these products generally comprise the addition of reactive materials to either the unpyrolyzed waste or to the volatile product to tie up these impurities. Alternately, the volatile pyrolysis products may be passed through a scrubbing (washing) tower in order to remove impurities. Elemental analysis of such pyrolysis oil reveals that it contains a significant amount of sulfur which reduces its value and usefulness in fuel applications and a higher level of nitrogen than found in diesel fuel.
In German Pat. No. 2,944,989 it is taught that by adding finely pulverized iron oxide to the volatile pyrolysis product, the sulfur pollutant is reduced.